Insomnia Severity Index (ISI)
Measures insomnia severity and its daytime impact over the past 2 weeks.
Last reviewed: July 2026
- Full name
- Insomnia Severity Index (ISI)
- Measures
- The Insomnia Severity Index was developed by Charles Morin to measure a patient's own perception of how severe their insomnia is over the past 2 weeks.
- Format
- 7 items · ~2 min · Self-report
- Score range
- 0 to 28
- Reliability
- Internal consistency is high (Cronbach's α ≈ 0.90–0.91 in community and clinical samples).
- Population
- Adults.
- Interpretation
- 0–7No clinically significant insomnia
- 8–14Subthreshold insomnia
- 15–21Moderate clinical insomnia
- 22–28Severe clinical insomnia
Scoring & Interpretation
Each of the 7 items is rated 0 to 4 and the ratings are summed for a total from 0 to 28. Higher scores mean more severe insomnia. A total of 8 or more marks subthreshold insomnia and 15 or more indicates clinical insomnia.
| Score Range | Severity | Clinical Action |
|---|---|---|
| 0–7 | No clinically significant insomnia | Within typical range; offer general sleep-hygiene advice if the patient has concerns |
| 8–14 | Subthreshold insomnia | Mild sleep difficulties — sleep-hygiene advice and monitor over time |
| 15–21 | Moderate clinical insomnia | Clinical insomnia — recommend formal assessment and CBT-I |
| 22–28 | Severe clinical insomnia | Major sleep disruption — urgent assessment and treatment |
- Internal consistency is high (Cronbach's α ≈ 0.90–0.91 in community and clinical samples).
- The ISI is sensitive to treatment change in CBT-I and pharmacotherapy trials, which makes it a standard outcome measure.
- A cut-off of 10 is optimal for detecting insomnia in community samples (86% sensitivity and specificity; Morin et al., 2011), while 15 identifies moderate-to-severe clinical insomnia.
- Original validation: Bastien, Vallières & Morin (2001).
When to Use This vs Alternatives
| Instrument | Measures | Items | Reach for it when |
|---|---|---|---|
| ISI This page | Insomnia severity & daytime impact | 7 | The comprehensive option you are reading about |
| PHQ-9 | Depression severity | 9 | The patient's main complaint is low mood, or you want to check whether the insomnia is part of a depressive episode rather than a primary sleep problem. The PHQ-9 measures depression severity and includes a sleep item; the ISI isolates and quantifies the sleep problem itself. |
| DASS-21 | Depression, anxiety & stress | 21 | You want to see whether depression, anxiety or stress is driving the sleep difficulty. The DASS-21 profiles all three; the ISI stays focused on how severe the insomnia is and how much it disrupts the day. |
| K10 | General psychological distress | 10 | You need a broad psychological-distress screen rather than a sleep-specific measure. The K10 flags general distress in ten items; the ISI tells you how severe the insomnia specifically is and whether it meets a clinical threshold. |
Insomnia severity & daytime impact · 7 items
Depression severity · 9 items
The patient's main complaint is low mood, or you want to check whether the insomnia is part of a depressive episode rather than a primary sleep problem. The PHQ-9 measures depression severity and includes a sleep item; the ISI isolates and quantifies the sleep problem itself.
Depression, anxiety & stress · 21 items
You want to see whether depression, anxiety or stress is driving the sleep difficulty. The DASS-21 profiles all three; the ISI stays focused on how severe the insomnia is and how much it disrupts the day.
General psychological distress · 10 items
You need a broad psychological-distress screen rather than a sleep-specific measure. The K10 flags general distress in ten items; the ISI tells you how severe the insomnia specifically is and whether it meets a clinical threshold.
See It in Action
Sample: a completed ISI, scored and interpreted.
How a completed ISI scores and interprets:
Moderate clinical insomnia.
On ClientForms the total and its severity band are scored for you and ready to read or export as a PDF.
See the dashboard view
Synthetic sample for illustration — not a real patient.
What It Measures
Its seven items cover the night-time complaints (difficulty falling asleep, staying asleep and waking too early), satisfaction with sleep, how noticeable the problem is to others, distress about it, and how much it interferes with daytime functioning. It maps onto the DSM-5 insomnia-disorder criteria of sleep dissatisfaction plus daytime consequences, so it captures how much the sleep problem bothers and impairs the person rather than logging objective sleep timing the way a sleep diary does.
When to Use the ISI
Use the ISI as a brief screen whenever a patient reports trouble sleeping, to quantify how severe the insomnia is and whether it crosses a clinical threshold. A total of 15 or more indicates clinical insomnia that warrants formal assessment and points toward CBT-I. Because it asks about the past 2 weeks, it is also well suited to tracking response to treatment over time.
Who It's For
Adults. The ISI is validated in clinical, primary-care and general-population samples, and is widely used as a treatment-outcome measure in CBT-I and medication trials. Self-report; clinician and informant versions also exist. Available in many languages.
Frequently Asked Questions
What does the ISI measure?
The Insomnia Severity Index (ISI) measures how severe a person's insomnia is over the past 2 weeks across seven items: difficulty falling asleep, staying asleep and waking too early, satisfaction with sleep, how noticeable the problem is to others, distress about it, and how much it interferes with daytime functioning. It captures the patient's perception of the problem rather than objective sleep timing.
How do you score the ISI?
Each of the seven items is rated 0 to 4 and the ratings are summed for a total from 0 to 28. Higher scores mean more severe insomnia: 0–7 is no clinically significant insomnia, 8–14 subthreshold, 15–21 moderate clinical insomnia and 22–28 severe.
What ISI score means someone has insomnia?
A total of 8 or more suggests subthreshold insomnia worth monitoring, and 15 or more indicates clinical insomnia that warrants formal assessment. A cut-off of 10 has been reported as optimal for detecting insomnia in community samples, but the score is interpreted in context rather than treated as a diagnosis on its own.
Should I use the ISI or a sleep diary?
They answer different questions. A sleep diary logs objective sleep timing night by night, such as when the patient went to bed, how long they took to fall asleep and how often they woke. The ISI measures how severe and distressing the insomnia feels and how much it impairs the day. Many clinicians use both: the diary to characterise the sleep pattern and the ISI to quantify severity and track change.
Where can I get the ISI, and is it free to use?
The ISI is free for clinical use (Morin) and is widely included in sleep and mental-health toolkits. On ClientForms you can send it to a patient, who completes it on their phone, and the total with its severity band comes back scored for you, ready to read or export.
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